There have been known bipolar secondary batteries each including a power generating element in which a plurality of bipolar electrodes are stacked with electrolyte layers and separators provided between the adjacent bipolar electrodes, the bipolar electrodes each including a positive-electrode active material layer formed on one of the surfaces of a current collector and a negative-electrode active material layer formed on the other surface. In other words, the bipolar secondary batteries have a structure in which the positive electrode active material layer, the electrolyte layer and the negative electrode active material layer form a unit cell layer, and a plurality of the unit cell layers are stacked with current collectors provided between adjacent unit cell layers.
In the bipolar secondary batteries, when an electrolyte containing an electrolyte solution such as a liquid electrolyte, a polymer gel electrolyte, or the like is used, a problem may occur in which the electrolyte solution leaks from one of the unit cell layers and comes in contact with the electrolyte solution of other unit cell layers, thereby causing liquid junction. In order to prevent the liquid junction, a technique of sealing each unit cell layer by disposing a seal portion to surround the periphery of each unit cell layer has been known (refer to Japanese Unexamined Patent Application Publication No. 9-232003).